A. FIELD OF INVENTION
This invention pertains to a novel knit material constructed and designed for a hook-and-loop type fastener, said material being stronger and longer lasting then previous such materials. The invention further pertains to a method of making said material.
B. DESCRIPTION OF THE PRIOR ART
Hook-and-loop fasteners are very popular for a large variety of applications because they have many properties which make them inherently more desirable then other types of fasteners. For instance, because these types of fasteners are made of woven or knit fabrics, they can be made of any color, are more decorative and they can blend easily with the base layers supporting the same. The fasteners are especially preferable for both infants and old people because they require much less physical dexterity then other types of fasteners (such as for example, buttons).
Typically, hook-and-loop fasteners consist of two facing flat components, each component being formed of a flat, usually ribbon-type base fabric which can be cut to any desired size. One of the components, the hook or male component includes a plurality of relatively stiff curved, open elements made of a monofilament yarn and extending away from the base fabric. The loop or female component consists of a plurality of pile type closed loops extending away from the base fabric so that when the two components are mated with each other, some of the hooks engage or pass through many of the loops thereby providing a coupling between the two components. When a normal force is applied between the two components, for example by pulling one of the components away from the other, the hooks separate from the loops.
Typically, the hooks were made in the prior art from a monofilament while the loops were made from a multifilament yarn (as described for instance in U.S. Pat. No. 5,267,453, incorporated herein by reference). The loop component was typically made using a two bar knitting machine and conventional napping and related processes.
A problem with existing hook-and-loop fasteners is that the loops wear off and/or are matted down easily and hence very soon there is insufficient ‘adherence’ between the two components. Therefore the fastener becomes ineffective because it is easy to peel and has low shear strength. A further disadvantage is that the existing fastener has a high proportion of yarn in the base of the fabric, rather than the pile. However since the primary function of the fabric is to provide the pile loops, this structure results in a fabric which is cost ineffective and has a weight which is not optimal for the physical performance.
One reason why the existing fasteners have poor cycle life is that the multifilament construction allows the loops to mat because of the fine denier of the loops which makes them easy to deform from the optimal erect position. Moreover, because standard loop components are made using a two bar knitting process, the resulting fabric has only a limited stability. However in some applications the component must be stable and rigid. Stability in these applications is achieved by applying additional bonding materials or foam. This step renders the loop component more expensive and adds the complication that it may delaminate.
Attempts to resolve this problem has included increasing the density and/or the weight of the yarns making up the loops however, this solution makes the fasteners more expensive. As discussed in more detail below, part of the problem with the existing fasteners is that the hooks engage only some of the filaments making up the loops. As a result, when the components are separated, the filaments are relatively weak and break. Therefore, after several uses, many of the loops become-open and the whole fastener becomes useless.